Though Bitcoin is a very promising commodity, still I think it cannot replace the real money. For one, any government will not hold anything that they cannot control and bitcoin for that matter is an example. It is a decentralized currency, meaning no one has a direct authority over it.
Real money is still real money. And i dont think a lot of normal people know about it. And both real world currency and the cryptocurrency are not going to be disappear from the world. All of them are going to play their role into this. And they are going to affect each other. But the crypto and private nature of the currency is going to make it harder for some currencies.